A technique for generating data by operating objects such as characters existing in a virtual three-dimensional space and performing perspective transformation on actions of the objects with a virtual camera has been widely used in three-dimensional video games. When two different actions are successively performed, the motion data of those different actions are blended during the transition from the former action to the latter action, to faithfully reproduce the actions of an object. The object is operated based on the blended motion data, so that the transition between the actions appears natural.
As the technique that is often used for blending such motion data, there has been a technique of blending the motion data related to the former action and the latter action while gradually varying the mixing ratio between the motion data related to the actions during the period in which those actions overlap with each other. Specifically, the motion combination ratio (motion blending ratio) is determined from the angles of rotation about the X-axis and the Y-axis, and reference actions are combined at the determined motion combination ratio, to generate motion data of a character. Based on the generated motion data, the character is operated (Patent Literature 1). According to some other method, the transition between two different actions is made to appear natural by spline interpolation.